A concussion is an injury to the brain. The brain does not work right for a while after a concussion. One may have problems with things like memory, balance, concentration, judgment, and coordination. The brain will need time to heal after a concussion. Most will have a full recovery with the proper rest and monitoring.
A concussion is caused by a sudden, violent jolt to the brain. It may be caused by:
A blow to the head
Severe jarring or shaking—like a bad fall
Abruptly coming to a stop—most common in car accidents
Concussions most often occur with events that involve:
                Motor vehicles        Bicycles        Skates, skateboards, and scooters        Sports and recreation        Falling down        Firearms        Physical violence such as                    Assault and battery            Domestic violence            Child abuse                        
Traumatic brain injury or concussions occur when the head sustains a blunt and powerful force. Though typically it is not the impact or bruising that causes the neurotrauma. It is the rapid motion of the head. When the head is spun violently or sent into a state of rapid acceleration followed by an abrupt stop, brain neuron functions are disrupted. In CTE (Chronic traumatic encephalopathy), this disruption has caused “Tau” proteins—structures commonly found in neurons—to progressively amass to toxic levels and form tangled structures within the brain. As a result, electrical signaling between neurons is diminished and the brain's ability to process and retain information becomes increasingly impaired. Emotional disorders such as dementia and depression may also ensue.
Historically, research on TBI (Traumatic Brain Injury) and CTE has focused on amateur and professional athletes. Initially diagnosed in boxers who had sustained multiple concussions in the ring, CTE is commonly associated with contact sports such as football, wrestling and ice hockey (in addition to boxing). Now, however, researchers are making a similar association between blast neurotrauma and CTE in U.S. military veterans who have served in war.
Over the last few years, safety concerns regarding football helmets and concussions have become a most pressing issue. Safety issues in football are now ubiquitous, ranging from increased safety measures in the NFL to academics rating the best football helmets. And now legislation is spreading across America aimed at treating student-athletes with concussions.
Football helmet manufacturers are very aware of this, which is why they have created the most innovative and advanced helmets the sport has ever seen. Helmets have radically transformed over the last 10 years into engineering marvels.
The drive to minimize head injuries in sports is stronger than ever, especially in football. The NFL, recognizing the importance, has put stricter player-safety rules and policies in place—but technology is catching up to offer preventive methods to combat the issue.
As described above, traumatic brain injury or concussions occur when the head sustains a blunt and powerful force that results in violent spun of the head or sending the head into a state of rapid acceleration followed by an abrupt stop. When this happen brain neuron functions are disrupted. Helmets are useful as safety gear to prevent brain injuries in an uncontrolled environment. If one can't prevent a crash or impact, but knows it will occur, a helmet can prevent or minimize injury to the head and brain. No helmet can protect against all possible impacts, and the impact may exceed the helmet's protection. No helmet protects any part of the body that it does not cover, so even if the head injury is minimized one may have a smashed face, broken bones or worse.
Standards define laboratory tests for helmets that are matched to the use intended. If a helmet can pass the tests for a sport or activity, it provides adequate impact protection. A construction helmet will not pass the more severe bicycle helmet tests. A bicycle helmet will not pass the more severe motorcycle helmet tests. None of them provides the protection against shrapnel that is required of a military helmet. Standards also define other tests for such parameters as strap strength, shell configuration, visor attachments, and the head coverage that must be provided, depending on the activity.
Helmets designed to handle major crash energy generally contain a layer of absorbable pad. When one crashes and hit a hard object, the pad part of a helmet crushes, controlling the crash energy and extending the head's stopping time by about few thousandths of a second to reduce the peak impact to the brain. Rotational forces and internal strains are likely to be reduced by the crushing.
Thicker pad is better, giving the head more room and milliseconds to stop. If the pad is 15 mm thick it obviously has to stop you in half the distance of a 30 mm thick pad. Basic laws of physics result in more force to the brain if the stopping distance is shorter, whatever the “miracle” pad may be. Less dense pad can be better as well, since it can crush in a lesser impact, but it has to be thicker in order to avoid crushing down and “bottoming out” in a harder impact. The ideal “rate sensitive” pad would tune itself for the impact, stiffening up for a hard one and yielding more in a more moderate hit.
If the helmet is very thick, the outer circumference of the head is in effect extended. If the helmet then does not skid on the crash surface, that will wrench the head more, contributing to strain on the neck and possibly to rotational forces on the brain. In short, there are always tradeoffs, and a super-thick helmet will probably not be optimal. It will also fail on consumer acceptance.
If there are squishy fitting pads inside the helmet they are there for comfort, not impact. The impact is so hard and sharp that squishy pad just bottoms out immediately. In most helmets a smooth plastic skin holds the helmet's pad together as it crushes and helps it skid easily on the crash surface, rather than jerking your head to a stop. In activities that involve forward speed on rough pavement, rounder helmets are safer, since they skid more easily. The straps keep the helmet on the head during the crash sequence. A helmet must fit well and be level on the head for the whole head to remain covered after that first impact.
The drawings referred to in this description should be understood as not being drawn to scale except if specifically noted.